Manufacture of fibroin solutions



Patented May 21, 1935 MANUFACTURE 2.002.0 3 or FIBROIN SOLUTIONS WilhelmIrion and Herbert Mahn, Dssau-in- Anhalt, Germany, assignors to I. .G.Farbenindustrie' Aktiengesellschaft, Frankfort -on-the Main," Germany NoDrawing. Application .February 2, 1932,

":Serial No. 590,507.

Our present invention relates to the manufacture of fibroin solutions. 1

One of its objects is to provide a process of concentrating aqueousfibroin solutions. Further objects will be seen from the detailedspecification following hereafter.

In the preparation of aqueous solutions of silk fibroin, fit forspinning, it is sometimes necessary to concentrate dilute solutions.This operation is often impaired by the partial or even completeseparation of the fibroin, with formation of a skin, similar to theformation of skin on hot milk.

For instance, when fibroin is dispersed in a sodium thiocyanate solutionas described in our copending application Ser. No. 531,850 filed April21, 1931 and the solution obtained is dialyzed until it contains lessthan 4 per cent. of salt, and the dialyzed solution is concentrated, askin is readily formed, particularly when the silk wastes have beensubjected to a mild pre-treatment in the d'egumming operation and thelike.

According to our invention the said separation of the fibroin is avoidedby adding to the solution a small quantity of bile or a. bile-acid,gallic acid amide, lecithin, an alkali salt of a hydroxy-, chlorooramino-benzoic acid, or a wetting agent, for instance, an alkali salt ofthe substituted naphthalin sulfonic acids, or an alkali salt of thesulfonated textile oils, such asTurkey red oil, or the like, in short byadding a substance known to have the effect of reducing surface tension.

Furthermore, the addition of such a substance allows omission of aspecial pro-treatment, except a careful degumming, of the silk wastes,before dissolving them, so that a degradation of the parent material isavoided. It also has the advantage that there are no jelly-likestructures and agglomerations to be removed from the solution, thatfiltration is facilitated, and that the resistance of the silk torubbing and to shearing is increased.

The following examples illustrate the invention:

Example 1.-An aqueous solution containing 4 per cent. of. fibroin and0.2 per cent. of sodium thiocyanate is mixed with 0.01 per cent. ofdesoxycholic acid and concentrated in a rotating drum, while it isheated to 30 C. to 40 C. and air is passed over it, to a fibroin contentof 18 to 20 per cent.

Example 2.An aqueous solution of fibroin containing about 4 per cent. offibroin and about 0.2 per cent. of sodium rhodanate is mixed with about0.05 per cent. of ox gall in a rotating drum. This mixture is heated atabout 30 to 40 C. and

In Germany February 2, 7 Claims. (01. 134-1) concentrated to a contentof about 18 to 20 per cent. of fibroin while passing air over thesolution.

Example 3.-The conditions are the same as in Example 2 with theexception that the ox gall is replaced by 0.02 per cent. of cholic acid.

Example air-An aqueous solution of fibroin containing about 6 per cent.of fibroin and about 0.4 to 0.5 per cent. of sodium rhodanate is mixedwith about 0.01 per cent. of desoxycholic acid in a rotating drum. Thismixture is heated at about 30 to 40 C. and concentrated to a content ofabout 18 to 20 per cent. of fibroin.

Example 5.-To an aqueous solution of fibroin containing about 4 to 5 percent. of fibroin and about 0.4 to 0.5 per cent. of sodium rhodanatethere are added about 1.5 per cent. of sodium salicylate. This solutioncan be concentrated under the conditions of the preceding examples to acontent of about 15 to 20 per cent. of fibroin without the formation ofa skin.

Example 6.-'Ihe conditions are the same as in Example 5 with theexception that the sodium salicylate is replaced by 1 per cent. of thesodium salt of isopropylnaphthalene sulfonic acid.

Our invention is not limited to the foregoing examples. Theconcentration of the dilute aqueous fibroin solutions may be carried outin any known manner. The temperature used in the concentrating operationmay vary within wide limits, it is, however, preferably not raised above40 C. in order to be sure that the fibroin molecule is degraded aslittle as possible.

What we claim is:

1. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to the dilute fibroin solution a compound'having thecapacity of reducing the surface tension of this solution and subjectingthe mixture to a concentrating operation.

2. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to the dilute fibroin solution a compound having thecapacity of reducing the surface tension of this solution and subjectingthe mixture toa concentrating operation at a temperature of at most 40C.

3. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to an aqueous solution of fibroin containing about 6 percent. of fibroin and about 0.4 to 0.5 per cent. of 7 per cent. offibroin by heating the said solution to about to- C. while passing airover it.

4. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to an aqueous solution of fibroin containing about 4 percent. of fibroin and about 0.2 per cent..of sodium rhodanate, about 0.05per cent. of ox gall in a rotating drum, and concentrating this solutionto a content of about 18 to 20 per cent. of fibroin by heating the saidsolution to about 30 to 40 C. while passing air over it. f g

5. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to an aqueous solution of fibroin containing about 4 percent. of fibroin and about 0.2 per cent. of sodium rhodanate, about 0.02per cent. of cholic acid in a rotating drum, and concentrating thissolution to a content of about 18 to' 20 percent. of fibroin by heatingthe said solution to about 30 to 40 C. while passing air over it.

6. In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to the dilute fibroin solution a surfacetension-reducing agent which is inert to the fibroin and is an organiccompound containing an acidic radical, the agent being added in a smallamount not materially in excess of about 2%, and subjecting the mixtureto a concentrating operationat a temperature below the temperature ofmaterial degradation of the fibroin.

'7; In the manufacture of aqueous fibroin solutions the steps whichcomprise adding to the dilute fibroin solution a surfacetension-reducing agent which is inert to the fibroin and is an organiccompound containing an acidic radical, the agent being added in a smallamount not materially in excess of about 2%, and subjecting the mixtureto'a concentrating operation at a temperature ofat most 40 C.

WILHELM IRION.

HERBERT MAI-IN. 20

